5.QT屏幕分辨率适配

#if(QT_VERSION >= QT_VERSION_CHECK(5,6,0))
        QApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif
        QApplication a(argc, argv);
        
        const float DEFAULT_DPI = 96.0;
        HDC screen = GetDC(NULL);
        FLOAT dpiX = static_cast<FLOAT>(GetDeviceCaps(screen, LOGPIXELSX));
        ReleaseDC(0, screen);
    float fontSize = dpiX / DEFAULT_DPI;
    
        QFont font = a.font();
        font.setPointSize(font.pointSize()*fontSize);
        a.setFont(font);